1. Field of the Invention
The present invention relates to a power cord having an insertion plug at one end of a cord, and its manufacturing method.
2. Description of the Prior Art
In a conventional power cord, for example, blades are connected to a plurality of conductors projected (exposed) from the leading end of cord, and the base side of blades and leading end side of cord are covered with vinyl chloride, and a plug is formed.
In this case of plug formed by vinyl chloride alone, it is excellent in forming performance and is inexpensive, but when the plug of vinyl chloride is inserted in the socket and left over for a long period, dust or moisture sticks to blades, and weak current begins to flow, and the resin texture is broken and a carbide conductive path may be formed to short-circuit blades, finally leading to outbreak of fire, and hence it had a problem of low reliability in tracking resistance.
Besides, since the plug is formed in one forming process (single forming process), shrinkage is likely to occur in thick wall portions, and the blade interval may be deviated by shrinkage.
Further, when the plug is formed of vinyl chloride, since vinyl chloride is relatively soft, it is likely to deform when inserting into or pulling out from the socket, and the blade interval may be deviated during such handling.